1. KEY CONCEPT Phenotype is affected by many different factors.

2. Phenotype can depend on interactions of alleles. • In incomplete dominance, neither allele is completely dominant nor completely recessive. • Heterozygous phenotype is intermediate between the two homozygous phenotypes • Homozygous parental phenotypes not seen in F1 offspring

3. Codominant alleles are neither dominant nor recessive. • The ABO blood types result from codominant alleles. • Codominant alleles will both be completely expressed. • Many genes have more than two alleles.

4. Order of dominance: brown > green > blue. Many genes may interact to produce one trait. • Polygenic traits are produced by two or more genes.

5. The environment interacts with genotype. • Phenotype is a combination of genotype and environment. • The sex of sea turtles depends on both genes and the environment • Height is an example of a phenotype strongly affected by the environment.